Gear trains are common mechanical systems generally formed by mounting a plurality of gears relative to each other such that teeth of adjacent gears engage one another. When designed properly, such gear trains may provide a smooth transmission of rotation from one gear to the next. The rotational speed and torque of each gear in a gear train may differ. For instance, a rotational speed of one gear in a gear train may differ from a rotational speed of an adjacent gear by a proportional rate known as a speed ratio. The speed ratio may be calculated by dividing the number of teeth of the input gear by the number of teeth of the output gear, or alternatively the radius of pitch circle of the input gear by the radius of pitch circle of the output gear. A torque of one gear in a gear train may also differ from a torque of an adjacent gear by a proportional rate known as a torque ratio. The torque ratio may be calculated by dividing the number of teeth of the output gear by the number of teeth of the input gear, or the radius of pitch circle of the output gear by the radius of pitch circle of the input gear.
While gear trains are well known and their operating properties widely praised, their performance while exposed to abrasive fluids leaves much to be desired. Specifically, abrasive fluids may work their way between meshing gear teeth rapidly wearing them away due to their repetitive engagement and disengagement. Gear teeth also generally require extensive machining to ensure smooth meshing between gears which may increase manufacturing costs. Thus, an alternative to a gear train capable of transmitting rotational motion, less susceptible to wear from abrasive fluids and easier to manufacture may be desirable.